In preliminary experiments strains of the human parasitic pathogen, Entamoeba histolytica, and of the reptilian pathogen, Entamoeba invadens, have been found to exhibit a chemotactic response to one or more of the following: commercial preparations of hydrolyzed proteins, washings from a rat large intestine and a casein solution after it had been incubated with live Entamoeba cells. The specific aims of this project are to further develop the techniques and conditions to assay Entamoeba chemotaxis; to identify a specific chemoattractant molecule; to determine the source and mechanism of generation of the chemotactic activity detected in rat colon washings and in casein solutions incubated with Entamoeba; and to characterize selected molecular events of Entamoeba chemotaxis. New chemotaxis procedures will be assessed for efficacy, and environmental conditions for chemotaxis assays will be optimized. A chemoattractant will be isolated from commercial protein hydrolysates by chromatographic techniques. An optimal small animal model will be sought to study the production of chemotactic activity in the intestine. The luminal contents, intestinal mucus and intestinal mucosa will be analyzed to determine the nature and sources of chemotactic activity. Experiments will determine if Entamoeba can generate an extracellular chemotactic activity by hydrolysis of nonchemotactic substances with secreted or intracellular enzymes. A cell surface chemoattractant receptor will be characterized by binding studies, and chemoattractant stimulated transmethylation reactions will be sought using radioactive labels. The long term objectives of this research are to enlarge our understanding of the behavioral physiology of this parasitic protozoan and to help explain the mechanisms of Entamoeba pathogenicity.